1. Field of the Invention
The field of the present invention is that of wiring and more particularly, that of wiring of aircraft and their fastening.
2. Description of the Related Art
The structure of an aircraft is conventionally achieved by a series of circular frames, supported by longitudinal frame members and positioned evenly along the fuselage, to which bars called stringers are fastened. The skin of the aircraft is attached to this network of frames and stringers.
The cells of aircraft, whether they be aeroplanes or helicopters, are conventionally made of metal which has a certain number of advantages. In particular, the conductive character of the metal makes it possible to achieve the following functions:                production of an electrical network for the return of current from the items of equipment of the aeroplane; the items of equipment are thus electrically connected, for the phase, to a wire carrying the electric current and, for the neutral, to the structure of the aircraft. There is therefore no need to put in place a specific current-return network.        common earthing of the items of equipment, which makes it possible to protect these items of equipment as well as the passengers,        creation of a common potential reference allowing the items of equipment to all have the same potential reference and to work in the same electrical voltage rate,        protection, by a Faraday cage effect, against the direct and indirect effects of lightning which could injure the passengers and destroy the items of electrical equipment on board, and finally        production of effective electromagnetic protection against electromagnetic radiation; specifically, when an electrical conductor is subjected to an electromagnetic field, a voltage, called an induced voltage, appears between its two ends and may cause interference, or even damage to the electrical receivers that are connected thereto. These electromagnetic fields may be created either by the radiation of an antenna or of a radar (particular directional radiation), or by circulation currents due to lightning strike and which will travel over the surface (which is more or less conductive) of the structure of an aeroplane (indirect effects of the lightning), or else by currents of high intensity which travel in the power cables of the internal electrical network of the aircraft.        
The technology of aircraft cells has however evolved and the designers are turning increasingly to the use of composite materials which have good performance with respect to weight and mechanical strength and in particular to the use of carbon fibre composites.
The result of this is that the functions indicated above are no longer performed, the electrical conductivity of these composite materials being relatively low. Moreover, in carbon fibre structures (or structures called CFRP), it is essential to prevent electric wires, even those in which low-intensity currents travel, from being able to come into contact with the structure. In case of breakage of a cable or a contact of this cable with the structure of the aeroplane, a short-circuit appears with which are associated a local heating and a possible catching-fire of the carbon and the resin contained by the structure. Such a phenomenon would cause the emission of fumes that are toxic for the passengers.
It is therefore necessary, on aircraft made of composite material, to recreate the functions formerly performed by the metal structure of the aircraft.
For this, a first change has been devised, which consists in installing along the structure of the aeroplane metal or metalized cable supports in the form of trunking elements in which the electric cables are attached. These linear trunking elements, with U section, run along the fuselage to perform the functions listed above and to protect the carbon structures from possible contact with a cable of a bundle that could be broken. An example of such trunking elements is given by European patent application EP 0184931 by British Aerospace.
In order to provide appropriate electromagnetic protection, it is important not to fill these trunking elements to more than 80%. However, trunking elements in the prior art do not allow expansion performing the basic protection functions.
It is important to recognize that the aeroplanes, whether at the time of their development or during their lifetime, evolve and that the quantity of electric cables that they contain can increase. It is therefore necessary to allow an increase in the volume of wiring in order to adapt to demand while maintaining the same electromagnetic protection.
On this matter, the British patent GB1354484 is known which proposes, when the trunking element is designed, the possibility of a lateral extension of the latter by installing a second trunking element capable of being deployed to the side of the basic trunking element. This configuration first of all has the drawback of having to virtually double the weight of the trunking element, even though the necessity for an extension is not yet apparent, and, above all, because of its means of attachment to the aeroplane wall, it is positioned with the opening of the trunking elements oriented towards the aircraft wall; because of this, it leaves the cables free inside itself and therefore does not tackle the problem of protection against short-circuits on aeroplanes made of composite material.